A laminated or sandwich-type structure containing a light weight interior member composed, e.g., of a porous body, such as a foam, or a corrugated or honeycomb member, has been adjudged to comprise the most appropriate configuration where light weight is of prime concern, but where the structure must also satisfy the required design and use constraints for a particular application. Typically, the sandwich-type structure will consist of an interior or core member composed of a porous body or having a corrugated or honeycomb geometry bonded between two exterior or face sheet members, the latter members commonly having flat surfaces. For example, organic or inorganic fiber reinforced epoxy or phenolic resins have been used as skin or face sheet members and rigid forms or foams prepared from such polymeric materials as polyurethane, polyvinyl chloride, epoxies, and phenolics have been employed as core elements. To illustrate, honeycomb and corrugated interior members have been fashioned from aluminum fiber and glass fiber reinforced plastics.
The use of organic materials as elements thereof self-evidently restricts the utility of such structures to relatively low temperature applications, commonly no higher than about 250.degree. C. Therefore, the primary objective of the instant invention was to fabricate sandwich-type structures which would be light weight, exhibit values of high strength, high stiffness, and high toughness, and be capable of use at high temperatures.